Prior work by the present inventors has established that highly halogenated metalloporphyrins are superior catalysts for the rapid and selective oxidation of hydrocarbons; (U.S. Pat. Nos. 4,970,348; 4,900,871; 4,895,682; and 4,895,680). The presence of fluoro, chloro and bromo substituents on the porphyrin ring is believed to cause enhancement of oxidative stability and increased catalytic activity. The mechanism of oxidation of hydrocarbon substrate, S, is believed to occur as follows, but the invention is not restricted to this mechanism: ##STR1##
Since it is necessary for two metalloporphyrin molecules to reductively bind the dioxygen molecule, the placement of both metal centers in the same molecule, as in a Gable porphyrin, would permit dioxygen binding between the metals, thereby enhancing the oxidation rate. The present invention concerns such a porphyrin and a process for using it to oxidize alkanes.
An ortho-Gable-porphyrin has been synthesized, see Meier, Kobuke and Kugimiya, J. Chem. Soc., Chem. Commun., 1989, 923, wherein the biszinc complex, with two mesotriphenylporphins joined at the fourth meso position of each ring to ortho positions of a phenylene radical, is prepared in 70% yield after chromatographic separation.